// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef CORE_INTERNAL_BWU_HANDLER_H_
#define CORE_INTERNAL_BWU_HANDLER_H_

#include <memory>
#include <string>

#include "absl/functional/any_invocable.h"
#include "connections/implementation/client_proxy.h"
#include "connections/implementation/endpoint_channel.h"
#include "internal/platform/byte_array.h"
#include "internal/platform/expected.h"

namespace nearby {
namespace connections {

// Defines the set of methods that need to be implemented to handle the
// per-Medium-specific operations needed to upgrade an EndpointChannel.
class BwuHandler {
 public:
  class IncomingSocket {
   public:
    virtual ~IncomingSocket() = default;

    virtual std::string ToString() = 0;
    virtual void Close() = 0;
  };

  struct IncomingSocketConnection {
    std::unique_ptr<IncomingSocket> socket;
    std::unique_ptr<EndpointChannel> channel;
  };
  using IncomingConnectionCallback = absl::AnyInvocable<void(
      ClientProxy* client,
      std::unique_ptr<IncomingSocketConnection> connection)>;

  virtual ~BwuHandler() = default;

  // Called by the Initiator to setup the upgraded medium for this endpoint (if
  // that hasn't already been done), and returns a serialized UpgradePathInfo
  // that can be sent to the Responder.
  // @BwuHandlerThread
  virtual ByteArray InitializeUpgradedMediumForEndpoint(
      ClientProxy* client, const std::string& service_id,
      const std::string& endpoint_id) = 0;

  // Called to revert any state changed by the Initiator to set up the upgraded
  // medium for an endpoint. Reverts for _all_ services. Use
  // RevertInitiatorState(service_id, endpoint_id) for a more fine-grained
  // approach.
  // @BwuHandlerThread
  virtual void RevertInitiatorState() = 0;

  // Called to revert any state changed by the Initiator to set up the upgraded
  // medium for an endpoint.
  // @BwuHandlerThread
  virtual void RevertInitiatorState(const std::string& service_id,
                                    const std::string& endpoint_id) = 0;

  virtual void RevertResponderState(const std::string& service_id) = 0;

  // Called by the Responder to set up the upgraded medium for this endpoint (if
  // that hasn't already been done) using the UpgradePathInfo sent by the
  // Initiator, and returns a new EndpointChannel for the upgraded medium.
  // @BwuHandlerThread
  virtual ErrorOr<std::unique_ptr<EndpointChannel>>
  CreateUpgradedEndpointChannel(
      ClientProxy* client, const std::string& service_id,
      const std::string& endpoint_id,
      const location::nearby::connections::BandwidthUpgradeNegotiationFrame::
          UpgradePathInfo& upgrade_path_info) = 0;

  // Returns the upgrade medium of the BwuHandler.
  // @BwuHandlerThread
  virtual location::nearby::proto::connections::Medium GetUpgradeMedium()
      const = 0;

  virtual void OnEndpointDisconnect(ClientProxy* client,
                                    const std::string& endpoint_id) = 0;
};

}  // namespace connections
}  // namespace nearby

#endif  // CORE_INTERNAL_BWU_HANDLER_H_